1. Field of the Invention
The present invention relates to an optical connector plug and an optical connector adapter as well as an optical connector for holding a front end of an optical fiber and optically connecting the optical fibers.
2. Description of the Related Art
In a related art, optical connection of optical fibers used in optical communication is carried out by a method of using an optical connector having an optical connector plug holding a front end of the optical fiber and an optical connector adapter for carrying out optical connection of the optical fibers by fixing the optical connector plugs, or a method of welding front end faces of the optical fibers.
According to the optical connection of the optical fibers achieved by a welding process, there is a problem that attachment and detachment of the optical connection of the optical fibers cannot be carried out and a problem that the welding steps are complicated, thereby restricting the use of the optical connector.
Further, according to an optical connector of an SC type, an FC type or the like for carrying out optical connection by using a cylindrical member for a ferrule holding an optical fiber and having an outer diameter of φ2.5 mm, the optical connector cannot be downsized and a wide mounting area is needed in mounting the optical connector to a mounting board.
Therefore, there has been proposed an MU type optical connector using a cylindrical member for a ferrule holding an optical fiber and having an outer diameter of φ1.25 mm and comparatively downsized (for example, refer to nonpatent literature 1 described below).
According to the MU type optical connector, an optical connector plug and an optical connector adapter are difficult to disengage from each other and reliability of optical connection can be promoted. However, such an MU type optical connector is generally designed to carry out optical connection using an optical fiber cord provided with a tension member and a coating further on an outer periphery of an optical fiber core line provided with a coating on an outer periphery of an optical fiber to carry out optical connection at a panel face on an outer side of an optical transmission apparatus. Therefore, a number of parts is large and downsizing thereof is difficult. Therefore, a wide mounting are is needed for mounting a comparatively small-sized MU type optical connector at a mounting board and there poses a problem that downsizing of the mounting board per se cannot be achieved.
Further, when the optical connector of the related art is mounted to the mounting board, the optical adapter is directly fixed to the mounting board and therefore, a space for attaching and detaching the optical connector plug holding the optical fiber is needed on the mounting board and there poses a problem that not only the mounting board is large-sized but also operational efficiency is poor.
Further, there is a problem that the conventional optical connector has a large number of parts and that integration of the optical connector flag and the optical connector adapter of the conventional optical connector is difficult to achieve.
In order to resolve such a problem, there has been proposed an optical connector for urging to hold a ferrule holding an optical fiber to a side of a front end face thereof in an axial direction by a leaf spring fixed to a mounting board to thereby bring the front end faces of the ferrules into contact with each other by predetermined pressure (for example, refer to patent literatures 1 and 2).                (patent literature 1)                    JP-A-2-259708 (pages 1 through 2, FIGS. 1 through 3)                        (patent literature 2)                    JP-UM-A-6-73705 (page 5, FIG. 1)                        (nonpatent literature 1)                    Japanese Industrial Standards (JIS) C5983 F14 type connector                        
However, according to the above-described optical connector using the leaf spring, there poses a problem that owing to durability performance of the leaf spring, when attachment and detachment are repeated, durability of the leaf spring is deteriorated, a deterioration in opposing connection of optical fibers, that is, a deterioration in insertion loss is brought about and therefore, a number of times of attachment and detachment is restricted.
Further, according to the above-described optical connector using the leaf spring, since there is no means for restricting movement of the ferrule holding the front end of the optical fiber in a rotating direction centering on an axis thereof, an eccentric direction of the core of the optical fiber cannot be prescribed and the inserting loss is increased by bringing about an eccentric shift of the core.
Further, according to the above-described optical connector using the leaf spring, there poses a problem that the ferrule is liable to disengage from the leaf spring by vibration and impact and the reliability is poor.
Further, according to the above-described optical connector using the leaf spring, the front end portion of the cylindrical body for ferrule is directly inserted into a sleeve for optical connection and therefore, there poses a problem that a defect is liable to be brought about at the polished front end face of the cylindrical member for ferrule when an inserting angle is large or by repeating attachment and detachment, the inserting loss in optical connection is liable to increase and the reliability is poor.